1. Field of the Invention
The present invention relates to a coil component and more particularly relates to a small and efficient transformer component.
2. Description of the Related Art
In recent years, a size reduction of a coil component has been strongly required due to a reason such as a substrate configuration of high density mounting and multilayer array, and at the same time it has been strongly required to reduce an electric current loss, more specifically to make efficiency higher.
In the past, a coil component which has been generally used is configured to have a ring-type core 103 that is made of a sintered compact of magnetic material, a flanged core 102, a coil 104 that is wound around a winding core of flanged core, and a resin base 105 in which metal terminals are buried as shown in FIG. 1A, for example, and a coil component 101 according to this configuration has such an advantage that a manufacturing cost of each constituent part is low and manufacturing stability is excellent (refer to Patent Reference 1).
However, when the ring-type core 103 and the flanged core 102 are assembled together, a magnetic flux leakage is not only generated naturally from a gap portion but also a magnetic flux leakage of no small quantity in magnetic flux Φx passing through an uppermost side and the vicinity thereof out of magnetic flux emitted from the flanged core 102 and absorbed into the ring core 103 as shown in FIG. 1B is generated at a seam of cores such as the one shown by X in this figure. In this case, an influence on electric characteristics (for example, inductance value and DC superimposed characteristic), which is caused by the magnetic flux leakage Φx from the gap portion, is calculated beforehand into a design of the coil component but the magnetic flux leakage Φx generated at the seam of cores is not calculated and becomes a main factor causing an error between an actual measurement value of the inductance and a design value thereof, and thereby there has been such a problem that a desired inductance value is not obtained.
Furthermore, due to a multilayer substrate array, there are also many cases in which a signal system circuit and the like are disposed in an upper portion of circuit substrate on which a coil component of power system such as a transformer component is mounted, and the magnetic flux leakage Φx generating from the seam of cores becomes a factor that causes a malfunction in signal processing electronic components mounted on the above-described signal system circuit.
Because of the above, it has been known to use a coil component 101′ that is configured to have a so-called bottomed cylindrical cup-shaped core as shown in FIG. 2A, for example, in order to suppress a magnetic flux leakage mainly from an upper portion of coil component and also a magnetic flux leakage from a seam of cores (refer to Patent Reference 2).
[Patent Reference 1] Japanese Published Patent Application No. H07-066042
[Patent reference 2] Japanese Published Patent Application No. 2000-082623